1. Field of the Invention
The present invention relates to methods for manufacturing semiconductor devices and, more particularly, to a method for manufacturing a thin layer of silicon carbide having a high degree of crystallinity with reduced crystal faults on a silicon substrate.
2. Description of the Prior Art
Epitaxial growth carried out on a silicon substrate is a technique used to obtain a silicon carbide crystal layer. The silicon carbide crystal layer obtained in this way is then used to form semiconductor devices therein. A manufacturing method for such a semiconductor device is described below.
First, a thin layer of a silicon substrate 2 is provided. Then the temperature of silicon substrate 2 is increased to the approximate range of 1100.degree. C. to 1200.degree. C. The silicon substrate is placed in a mixture consisting of hydrogen gas serving as carrier gas and a few percent of a source gas (for example, SiH.sub.4, SiH.sub.6 or SiH.sub.2 CL.sub.6), whereby a silicon carbide crystal layer 3 is epitaxially grown on the silicon substrate 2, as shown in FIG. 1. Changing the concentration of the source gas serves to control thickness of the silicon carbide crystal layer 3. The silicon carbide crystal layer 3 thus obtained is used to form semiconductor devices (not shown) therein.
However, the conventional technique described above suffers from certain drawbacks. It is by heteroepitaxial growth that the silicon carbide crystal layer 3 is formed onto the silicon substrate 2. Consequently, there are differences between the silicon substrate 2 and the silicon carbide crystal layer 3 with regard to the lattice constant, the thermal expansion coefficient and chemical binding. As a result, the silicon carbide crystal layer 3 formed thereby has crystal faults, above all, stacking faults. These faults deteriorate the electrical characteristics of circuit devices formed in the silicon carbide crystal layer 3 and cause problems for its application as a semiconductor circuit.